Thrombolysis vs Primary Angioplasty for STEMI: When to Refer

Choosing between thrombolysis and primary angioplasty for ST-elevation myocardial infarction (STEMI) turns on time. Primary angioplasty is the treatment of choice whenever a catheterisation laboratory (cath lab) and a cardiologist can be reached within 90 to 120 minutes. When they cannot, the patient should be thrombolysed: ideally within 30 minutes of arriving at hospital, within 12 hours of symptom onset, and only after contraindications and aortic dissection have been excluded.

That rule, set out by Dr. Rohit Goel, Principal Consultant, Cardiology at Max Hospital, Gurugram, India, at the time of the session (currently Associate Director - Cardiology at Max Hospital, Gurugram, India), is written for the doctor who receives a heart attack patient in a hospital without an interventional cardiology service. Both strategies have the same purpose: to reopen a completely blocked coronary artery before the heart muscle it supplies dies. They differ in how reliably they achieve it, what they cost, and who can safely receive them. This article covers both, the decision between them, and what to do when neither is possible. The drug protocol that every patient receives first is in the complete guide to ischaemic heart disease.

Why reperfusion cannot wait

Reperfusion means restoring blood flow through the blocked artery. Dr. Goel put mortality in STEMI at up to 30 to 50% when the condition is not treated properly. The ECG signature of STEMI, ST elevation, persists for as long as the artery stays completely blocked, for up to 48 hours. Until the artery is opened, the muscle it supplies remains at risk.

The practical consequence is that the diagnosis of STEMI is made on the ECG alone. Dr. Goel was explicit that cardiac biomarkers have no role in the decision to thrombolyse, because they may not yet be detectable in the first hours: if the ECG shows ST elevation or a new left bundle branch block, the doctor should not wait for the blood test. The reasoning behind that rule is covered in the companion article on ECG and cardiac biomarkers.

Primary angioplasty for STEMI: the treatment of choice

Primary angioplasty, also called primary percutaneous coronary intervention (PCI) or primary PTCA, is emergency angioplasty performed as the first reperfusion treatment for STEMI. Once STEMI is diagnosed, Dr. Goel's instruction is to refer the patient immediately for coronary angiography if a catheterisation laboratory and a cardiologist are available. Angiography shows the exact blockage; if the artery is 100% blocked, it is opened with a balloon, a stent is placed, and the patient is stabilised.

He illustrated the procedure with two angiograms. In the first, the right coronary artery was completely blocked; after a stent was placed, the artery was fully open and blood flow re-established. In the second, a tight 95% narrowing of the left anterior descending artery was causing the heart attack, and it too was opened with a stent, restoring normal flow.

Primary angioplasty should be done in a catheterisation laboratory by a cardiologist. Its advantage over thrombolysis is certainty: the artery is seen on angiography, opened and stented, and the residual narrowing that caused the event is treated at the same time. Cost guidance for the procedure is on the angioplasty with stent cost page.

Thrombolysis vs primary angioplasty: the 90 to 120 minute rule

The decision between thrombolysis and primary angioplasty turns on transfer time to a cath lab. Dr. Goel's threshold:

• If the patient can reach a hospital with a catheterisation laboratory within 90 to 120 minutes, refer for primary angioplasty.
• If transfer will take longer, or no such facility exists, thrombolyse the patient where they are.

While the decision is being made, the patient receives the emergency drug protocol: intravenous access, oxygen, aspirin with a P2Y12 inhibitor (ticagrelor 180 mg if possible, otherwise clopidogrel or prasugrel), atorvastatin or rosuvastatin, and morphine or sublingual glyceryl trinitrate for pain. Heparin is also given in STEMI.

Who should receive thrombolysis

Thrombolysis means dissolving the clot with an intravenous drug. It is given only to patients with STEMI or new-onset left bundle branch block (a block in the heart's electrical conduction to the left ventricle); patients with non-ST-elevation myocardial infarction (NSTEMI) or unstable angina are never thrombolysed. Dr. Goel's criteria for thrombolysis are:

1. A good clinical history consistent with a heart attack.
2. Symptom onset less than 12 hours earlier.
3. An ECG showing ST elevation or new left bundle branch block.

Thrombolysis should ideally begin within 30 minutes of the patient's arrival at hospital. This matches the 30-minute door-to-needle target in American (ACC/AHA) guidance.

Thrombolytic drugs: streptokinase, alteplase, reteplase and tenecteplase

In practice the main thrombolytic molecules are four: streptokinase, alteplase, reteplase and tenecteplase, because urokinase is usually not available. Dr. Goel's comparison:

• Streptokinase is the cheapest, but its efficacy is lower.
• Alteplase, reteplase and tenecteplase have very good efficacy, better than streptokinase, but they are more expensive.

His advice to emergency departments was to keep at least one of these molecules in stock, so that eligible patients can benefit without delay.

The standard regimens in mainstream STEMI guidance (ESC) are:

Fibrin-specific agents (alteplase, reteplase and tenecteplase) are given with an anticoagulant such as heparin.

Contraindications to thrombolysis

Thrombolytics dissolve clots everywhere in the body, not only in the coronary artery, so the main danger is bleeding. Before giving one, Dr. Goel takes a history against a checklist. Thrombolysis should not be given in the presence of:

• A recent stroke, less than two months old.
• Any previous haemorrhagic stroke.
• Head trauma in the last four weeks.
• Recent surgery, including dental extraction, in the last two weeks.
• Lumbar puncture within the last four weeks.
• Active peptic ulcer or any other cause of gastrointestinal blood loss.
• Concurrent anticoagulation, unless the INR (a blood test of how long blood takes to clot) is below 2.
• Liver disease or a clotting disorder.
• Pregnancy.
• Acute pancreatitis.
• Aortic dissection.
• Active pulmonary tuberculosis with cavities in the lungs.
• Oesophageal varices.
• A brain tumour.
• Blood pressure above 200/120 mmHg.

The ESC guideline lists an ischaemic stroke in the previous six months as an absolute contraindication and treats uncontrolled hypertension above 180 mmHg systolic or 110 mmHg diastolic as a relative contraindication. In any of these situations, Dr. Goel's alternatives are primary angioplasty or medical management.

Two items on the list need emphasis. Aortic dissection can mimic STEMI, and thrombolysing it can extend the tear and cause sudden cardiac arrest, as explained in the diagnosis article. Pregnant women with STEMI are referred for primary angioplasty instead of being thrombolysed.

STEMI when neither angioplasty nor thrombolysis is possible

A STEMI patient who can be neither thrombolysed nor transferred for angioplasty has a poor prognosis, in Dr. Goel's assessment, and is managed medically in intensive care. Ideally, a patient who cannot be thrombolysed should be sent for primary angioplasty. If that is also impossible, Dr. Goel uses whatever resources the intensive care unit has:

• aspirin with clopidogrel or ticagrelor
• a statin
• a beta blocker
• an ACE inhibitor
• nitrates
• heparin or low molecular weight heparin

He described the outcome as roughly 50/50. Some patients respond very well to medical treatment; others deteriorate, and those who deteriorate must be referred to a higher-level centre.

Treatment after reperfusion

Once the artery has been opened, by angioplasty or by thrombolysis, the patient continues dual antiplatelet therapy, a statin and a beta blocker, with an ACE inhibitor where indicated, an echocardiogram and a cardiac rehabilitation programme. After thrombolysis, guidelines also recommend transfer to a centre with a catheterisation laboratory: immediately for rescue angioplasty if the ST elevation has not fallen by at least half within 60 to 90 minutes or the patient is unstable, and otherwise for routine angiography within 2 to 24 hours. The full post-reperfusion regimen and the rehabilitation framework are set out in the complete guide.

A reperfusion checklist for hospitals without a catheterisation laboratory

Drawn together, Dr. Goel's guidance gives the receiving doctor a clear sequence:

1. Record a 12-lead ECG immediately. ST elevation or new left bundle branch block means STEMI.
2. Do not wait for cardiac biomarkers before deciding on reperfusion.
3. Start the emergency drug protocol: aspirin, a P2Y12 inhibitor, a statin, pain relief and heparin.
4. Exclude aortic dissection on history and chest X-ray.
5. Ask whether a catheterisation laboratory can be reached within 90 to 120 minutes. If yes, transfer for primary angioplasty.
6. If not, check the contraindications and, if none applies and symptoms began less than 12 hours earlier, thrombolyse, ideally within 30 minutes of arrival, then transfer for angiography within 2 to 24 hours, or immediately if thrombolysis fails.
7. If thrombolysis is contraindicated and transfer impossible, manage in intensive care and refer if the patient deteriorates.

Referring doctors' questions on prognosis without thrombolysis, glycoprotein IIb/IIIa inhibitors and aortic dissection are answered in the Live Discussion, and Dr. Goel's background is on his doctor profile. For when bypass surgery is preferred over a stent in stable disease, see Dr. Biswarup Purkayastha's article on left main coronary artery disease, and for hospital protocols across the acute coronary syndrome spectrum, Dr. Vikas Thakran's article on STEMI and NSTEMI management protocols. More heart care articles are on the cardiology specialty page.